Hearthstone’s May 2015 Ranked Play Season: Go Ninja, Go! is coming to a close at the end of the month, and your chances of acquiring the Ninja card back for your collection will soon come to an end!
This stealthy card back will only be available during May, so be sure to hit Rank 20 before the 1st of June and the card back will be awarded to you at the end of the season.
The June 2015 season—and a new card back along with it—await you next month!